1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "base/memory/shared_memory.h" 6 7 #include <stddef.h> 8 #include <sys/mman.h> 9 10 #include "base/logging.h" 11 12 #if defined(__ANDROID__) 13 #include <cutils/ashmem.h> 14 #else 15 #include "third_party/ashmem/ashmem.h" 16 #endif 17 18 namespace base { 19 20 // For Android, we use ashmem to implement SharedMemory. ashmem_create_region 21 // will automatically pin the region. We never explicitly call pin/unpin. When 22 // all the file descriptors from different processes associated with the region 23 // are closed, the memory buffer will go away. 24 Create(const SharedMemoryCreateOptions & options)25bool SharedMemory::Create(const SharedMemoryCreateOptions& options) { 26 DCHECK_EQ(-1, mapped_file_ ); 27 28 if (options.size > static_cast<size_t>(std::numeric_limits<int>::max())) 29 return false; 30 31 // "name" is just a label in ashmem. It is visible in /proc/pid/maps. 32 mapped_file_ = ashmem_create_region( 33 options.name_deprecated == NULL ? "" : options.name_deprecated->c_str(), 34 options.size); 35 if (-1 == mapped_file_) { 36 DLOG(ERROR) << "Shared memory creation failed"; 37 return false; 38 } 39 40 int err = ashmem_set_prot_region(mapped_file_, 41 PROT_READ | PROT_WRITE | PROT_EXEC); 42 if (err < 0) { 43 DLOG(ERROR) << "Error " << err << " when setting protection of ashmem"; 44 return false; 45 } 46 47 // Android doesn't appear to have a way to drop write access on an ashmem 48 // segment for a single descriptor. http://crbug.com/320865 49 readonly_mapped_file_ = dup(mapped_file_); 50 if (-1 == readonly_mapped_file_) { 51 DPLOG(ERROR) << "dup() failed"; 52 return false; 53 } 54 55 requested_size_ = options.size; 56 57 return true; 58 } 59 Delete(const std::string &)60bool SharedMemory::Delete(const std::string&) { 61 // Like on Windows, this is intentionally returning true as ashmem will 62 // automatically releases the resource when all FDs on it are closed. 63 return true; 64 } 65 Open(const std::string &,bool)66bool SharedMemory::Open(const std::string&, bool /*read_only*/) { 67 // ashmem doesn't support name mapping 68 NOTIMPLEMENTED(); 69 return false; 70 } 71 72 } // namespace base 73